This invention relates to an ultrasonic bathing system.
Ultrasonic bathing systems have been known for some time. One such system is described in U.S. Pat. No. 5,048,520 of Sep. 17, 1991. This patent claims to describe an ultrasonic bathing system employing a power level of between 0.1 and 5 watts per square centimeter at a time of less than 15 minutes, with the frequency being swept through a predetermined sweep frequency band. The alleged reason for employing a swept frequency generator is that if a constant frequency is employed, standing waves will be set up within the bathtub and these will cause distributed regions of high and low intensity within the bathing fluid.
The above patent makes several claims concerning the germicidal effects of ultrasonic systems and also the significance of cavitation about which the present applicants are skeptical. Nonetheless, it is believed that the establishment of ultrasonic waves within a bathing fluid can serve to exert a mechanical cleaning action on an immersed item, whether it be a mechanical component or a human body. The advantage of ultrasonic systems, as opposed to pumped flow systems, is that after each use the bathing fluid can be completely drained from the bathtub. There are no pipes connecting the bathtub to a pumping system that can serve to retain harmful bacteria.
While ultrasonic bathing systems have certain advantages over conventional whirlpool systems, a problem remains as to how to adjust the power level of the ultrasonic energy within the bathing system without effecting the cleaning efficiency. If a conventional signal generator is employed and the power level turned down, this merely reduces the amplitude of the wave applied to the bathing system.
Since the cleaning action of ultrasonic energy is dependent on the resulting mechanical agitation, the agitation caused by the wave is less at a lower amplitude and the cleaning efficiency suffers. Indeed, below certain power levels, the ultrasonic energy is really insufficient to create a mechanical cleaning action. Yet, there are many situations where it is desirable to reduce the overall power level. For example, elderly patients or patients with serious wounds may require more gentle treatment than patients having a stronger constitution. The problem is, that treatment at a reduced power level may in fact be no treatment at all if the mechanical agitation caused by the ultrasonic energy is insufficient to dislodge attached debris.